The term “carbonylation” generally refers to chemical reactions that introduce carbon monoxide molecules into other organic and inorganic substrate molecules. Carbonylation results in a substrate molecule gaining a carbonyl functional group. Carbonylation reactions are important in industrial chemistry and are becoming a more important building block for fine and bulk chemicals. Specifically, catalytic carbonylation of cyclic compounds including epoxides, aziridines, thiiranes, oxetanes, lactones, lactams, and analogous compounds is useful for the synthesis of the ring expanded products of such compounds.
Further commercial and industrial benefit may result in modifying cyclic compounds through a process known as ring opening polymerization which is a form of chain-growth polymerization. In ring opening polymerization, the terminal end of a polymer chain acts as a reactive center where further cyclic monomers can react by opening cyclic rings and forming a longer polymer chain. Under certain conditions, ring-opening polymerization can proceed via radical, anionic or cationic polymerization. Certain beta-lactone molecules, such as beta-butyrolactone, beta-valerolactone, beta-heptanolactone, beta-tridecanolactone, cis-3,4-dimethyloxetan-2-one, 4-(butoxymethyl)-2-oxetanone, 4-[[[(1,1-dimethylethyl)dimethylsilyl]oxy]methyl]-2-oxetanone, and 4-[(2-propen-1-yloxy)methyl]-2-oxetanone, 4-[(benzoyloxy)methyl]-2-oxetanone to name a few, may undergo ring opening polymerization to produce certain polylactones.
Polylactones, including polypropiolactone, polylactide, polyglycolide, and polycaprolactone, may be characterized as biodegradable polymers. Polylactones are generally stable, have low toxicity, and may be easily transported and stored at remote locations. Recent advances in the carbonylation of epoxides—such as in U.S. Pat. No. 6,852,865—and the ring opening polymerization of beta-propiolactone intermediates has provided more efficient synthetic routes to polylactones. The recent advances in the production of polylactones combined with certain physical and chemical properties make the polylactones ideal for many commercial and industrial applications. However, conventional processes may be less effective at producing highly pure polylactones. Certain polylactones may be thermally decomposed through a process known as thermolysis.
Generally, thermolysis is a chemical decomposition process in which heat causes the cleavage of one or more covalent bonds. In at least one mechanism for thermolysis of polymers, heat converts a polymer of chain length n into a polymer of chain length n−1 and produces a molecule of an organic acid.